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USB-Serial Adapter shows up as /dev/ttyACM0 instead of /dev/ttyUSB0

Posted: Wed Jan 16, 2019 2:06 am
by rwh
I'm trying to use the Freetronics USB-Serial Adapter to reflash a Sonoff POW2 using Ubuntu 18.10, however I'm not having any luck getting esptool to talk to it. When I plug in, I see this in dmesg:

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[2401020.558825] cdc_acm 1-8:1.0: failed to set dtr/rts
[2401278.910987] usb 1-8: new full-speed USB device number 9 using xhci_hcd
[2401279.061233] usb 1-8: New USB device found, idVendor=26ba, idProduct=0003, bcdDevice= 0.01
[2401279.061235] usb 1-8: New USB device strings: Mfr=1, Product=2, SerialNumber=220
[2401279.061236] usb 1-8: Manufacturer: www.freetronics.com
[2401279.061237] usb 1-8: SerialNumber: 757353534383517122B1
[2401279.062950] cdc_acm 1-8:1.0: ttyACM0: USB ACM device
I see /dev/ttyACM0 appear, and I can chmod it so I can use it:

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sudo chmod o+rw /dev/ttyACM0
However, esptool refuses to talk to it:

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esptool --port /dev/ttyACM0 read_flash 0x00000 0x100000 sonoff-backup.bin
esptool.py v2.1
Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____

A fatal error occurred: Failed to connect to Espressif device: Timed out waiting for packet header
I note that esptool assumes the device will be on /dev/ttyUSB0, and I've googled for a few hours and tried a bunch of tricks to try to make the kernel show the device as /dev/ttyUSB0, but to no avail.

It seems to work fine on a Windows 10 VM, showing up as a "USB Serial Device (COM3)", but also will not communicate with the Sonoff:

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python esptool.py read_flash 0x00000 0x100000 sonoff-backup.bin
esptool.py v2.6
Found 1 serial ports
Serial port COM3
Connecting........_____....._____....._____....._____....._____....._____....._____
COM3 failed to connect: Failed to connect to Espressif device: Timed out waiting for packet header

A fatal error occurred: All of the 1 available serial ports could not connect to a Espressif device.
Am I just missing something really obvious?

Thanks,

Rob